2292: Thermometer

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I hate how many times you have to press it to get to the system normal people use, degrees Rømer.
Title text: I hate how many times you have to press it to get to the system normal people use, degrees Rømer.


This comic is the 17th comic in a row (not counting the April Fools' comic) in a series of comics related to the COVID-19 pandemic.

This comic expresses frustration at the multitude of temperature scales. Randall, as a former engineer, has strong opinions about units, as unit conversion is often a gripe for many engineers. (In a special preface in the UK edition of Randall's book What If, he mentions that one does not appreciate the metric system unless they have had to go through a bunch of scientific papers using really unusual units like "kilocubic feet per second" or "acre-feet".) As elevated body temperature is a symptom of COVID-19, the comic is thus also concerning the virus.

Cueball is holding what appears to be a medical thermometer, implying that he's trying to check his body temperature. He mentions that the thermometer is in Celsius, and asks how to change it. Many thermometers sold in the United States have settings for both Fahrenheit and Celsius, with an option to change between the two. Americans are almost always more familiar with body temperatures in Fahrenheit, so Cueball presumably expects to change to that scale. However, he finds that the thermometer provides measurements in a series of scales that are increasingly unhelpful. Human body temperature in Celsius is 37 °C.

  • Degrees Celsius are used in most of the world. The Celsius scale sets 0 degrees to water's freezing point and 100 degrees to water's boiling point. Few Americans have a clear idea of what normal and elevated ranges of human body temperature are in Celsius.
  • Kelvin is a unit often used in scientific fields. It is calibrated on the same scale as degrees Celsius, but 0 K is set at absolute zero or -273.15 °C. This is used in scientific or engineering contexts requiring a thermodynamically absolute temperature, such as Charles's law, but almost never in a medical context, making the report of little use.
  • The Rankine scale is another absolute scale, with its zero set at absolute zero, but degrees identical to degrees Fahrenheit. While this scale is still occasionally used in some industrial and scientific settings (being more convenient for absolute temperatures in a system including Fahrenheit), it's essentially never used in medicine, and most people have never heard of it.
  • Thermodynamically, temperature is the average translational kinetic energy of a group of particles. Translational kinetic energy means it doesn’t include rotational and vibrational kinetic energy. The relation between a gas’s translational kinetic energy E and its temperature T is
E=\frac32 k_B T,
where kB is the Boltzmann constant, 1.380649×10−23 J⋅K-1. So if this thermometer told you a translational kinetic energy measurement in joules, you could get the measured temperature in the Kelvin scale by dividing by the Boltzmann constant and multiplying by 2/3. Somebody who actually wanted to use this measure of temperature might then find it useful to have Boltzmann's constant printed on the thermometer.

Using these last three units for home temperature gauging would be ridiculous, as Kelvin and Rankine measurements of body temperature are unfamiliar to the average user and even those familiar with them would need to do calculations to translate normal body temperature. Kinetic energy is obscure enough that only physicists, engineers and thermodynamicists, a relative handful of the potential buyers, would likely know what it refers to. Those that do could make use of the value printed on the thermometer, but such would add a great deal of unnecessary complexity to what should be a simple and intuitive task.

In the last frame Cueball calls the thermometer the worst. It seems to lack Fahrenheit entirely, frustrating its American consumer base, including Cueball. From a nerd's perspective this would be an extraordinary device, offering even exotic temperature scales. However, a "normal person" would find this thermometer terribly difficult to use for everyday purposes when set on any of the non-Celsius scales, like checking their body temperature or the temperature of food. As an item of consumer electronics, especially one sold in the United States, it would be almost completely useless.

Deliberately lacking Fahrenheit is a jab against the Imperial system of units, and against the similar but distinct system of United States customary units. Although Imperial units and local traditional units are still used for various limited purposes (and/or by older generations) in different countries, most of the world has switched to using the metric system for most purposes going forward, with the US being relatively unusual in the extent to which it still routinely defaults to the US customary units in daily life. Many proponents of the metric system have long pushed for the US to change over, arguing that Imperial and US customary units (and degrees Fahrenheit, specifically) are archaic and obsolete. Randall has dealt with this conflict in other strips; as a physics major, he's partial to the metric system, and finds it frustrating to maintain multiple different scales (which is the basis of the conflict in this strip). On the other hand, he recognizes certain intuitive advantages to Imperial and US customary measurements, and recognizes that the forces of social inertia in US society make change difficult.

The title text references an archaic temperature unit, Rømer, first proposed in 1701. It is the common ancestor of both the Celsius and Fahrenheit scales, defining the freezing point of water as 7.5 degrees and the boiling point of water as 60 degrees. Unlike the other measurements mentioned in this strip, the Rømer scale is no longer used in any context, and only people interested in the history of temperature scales have any idea that it even exists. This is the ultimate form of obscure and outdated temperature measurements.


[Cueball stands in the center of the panel holding a thermometer.]
Cueball: This thermometer is in Celsius. How do you change it?
Off-panel voice: Long press the button.
[Cueball presses the button, and the thermometer beeps]
Thermometer: Units: Kelvin
Cueball: No...
[Cueball presses the button, and the thermometer beeps]
Thermometer: Units: Degrees Rankine
Cueball: What.
[Cueball presses the button, and the thermometer beeps]
Thermometer: Units: Average Translational Kinetic Energy
Cueball: This is the worst thermometer.
Off-panel voice: Boltzmann's constant is on the side if you need it.


In 1643: Degrees, Cueball struggles with which temperature unit to use, and ultimately tells his friend the temperature in radians, which is not a valid temperature scale.

In 1923: Felsius, Randall proposes a combined Fahrenheit/Celsius temperature scale called Felsius.

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First non-Covid post other than April fools? 23:04, 10 April 2020 (UTC)

Since a fever is a common symptom of Covid-19, I'd say this is as much about Covid-19 as all the previous comics on the topic. Ianrbibtitlht (talk) 02:59, 11 April 2020 (UTC)
I'd disagree. Fevers aren't inherently related to COVID-19, and while it's certainly easy to draw a connection based on current events, at no point is the connection made explicit. 10:29, 11 April 2020 (UTC)
Seriously? Fever is associated with 88% of COVID-19 cases! I'd say that's inherently related, and I'm drawing a connection based on that fact. Ianrbibtitlht (talk) 12:59, 11 April 2020 (UTC)
Fevers are associated with almost all infectious diseases. By that logic, this could be about the flu, mono, or a hundred other conditions. Shamino (talk) 17:24, 11 April 2020 (UTC)
I, too, think calling this a Covid-19 comic is excessive. Sure, thermometers for measuring body temperature are sold out at my local drugstore, and pandemic likely inspired the comic, but if it had been published a year ago, we wouldn't infer any connection to a specific disease or global epidemic. - Ada in New Hampshire, USA 07:56, 12 April 2020 (UTC)
I would assume anything that can be linked, even loosely, is probably part of this chain. I have been assuming since the 6th one that Randel would aim for 19 of these just because. Though perhaps he will keep going till the hype is over. Either way, requiring that it directly mentions the topic it was inspired by would be way overkill. Mentioning things that likely inspired a comic is something we have done for a long time, and the virus seems like the most likely inspiration, especially when taking the full comic chain into account172.69.198.52 21:33, 12 April 2020 (UTC)
Also there has been a run on thermometers over the last few weeks. I don't know what it's like in the US, but definitely in Europe it's hard to find a thermometer for human use now. Everyone has been buying them, and obviously for many people they have been buying them for the first time ever. 17:56, 13 April 2020 (UTC)
The comic doesn't mention a fever. For all we know Cueball is trying to measure the outside air temperature, or how hot his coffee is. We can rule out the idea that he is trying to measure the temperature of some liquid helium only because he skipped past the kelvin scale. Jeremyp (talk) 18:39, 12 April 2020 (UTC)
The shape of the thermometer in the comic is very definitely the shape of a thermometer for human use. And not the shape of a thermometer for household or garden use. These thermometers typically have one button ("the button"). Changing the units typically requires a long press on that button... What more do you need? 17:56, 13 April 2020 (UTC)

A common practice in schools and the like prior to quarantine was temperature taking upon arrival. So it's like that this comic continues that to the home setting. 23:19, 10 April 2020 (UTC)

A pessimist would guess that this means someone in Randall's household has a fever. 23:26, 10 April 2020 (UTC)

> The Physician Ducks172.69.62.94 23:32, 10 April 2020 (UTC)

Personally I'd welcome a home thermometer marked off in Kelvin, avois all the "twice as cold" sort of confusion you can get with an arbitrary zero as used in Celsius and Fahrenheit. 23:21, 10 April 2020 (UTC)

I might have enjoyed a "Degrees of Kevin Bacon" joke in this comic somewhere. :-) 23:42, 10 April 2020 (UTC)

Double-plus-dissapointed we didn't get the Delisle measure referenced at all... 01:17, 11 April 2020 (UTC) ...and now added. It would be better in any Trivia section, but we don't have one so hoping it's no more out of place in the explanation as Fahrenheit. 02:02, 11 April 2020 (UTC) ...aaaand someone removed it (as pure trivia, of course), fair enough. Anticipated. Anyone still interested in what I put just needs to check this IP, at about this timestamp, in Page History, though, so not going to argue the point. 02:08, 11 April 2020 (UTC)

No temperature scale is defined using melting or boiling points of water anymore. Since 2019 Kelvin is defined via the Boltzmann constant, and all other temperature scales have been (re-)defined relative to the Kelvin scale for quite a while. -- 01:24, 11 April 2020 (UTC)

Randall forgot the Réaumur scale. 03:00, 11 April 2020 (UTC)

I'm not sure why some people seem to look for any opportunity to take a dig at the US, but I removed the line in the explanation about US-based readers not being familiar with the Celsius temperature scale. I'm sure most Americans are familiar with it but prefer the Fahrenheit scale instead. I don't understand why anyone holds that against us. Ianrbibtitlht (talk) 03:04, 11 April 2020 (UTC)

Hey, let's assume good faith. Chances are, some rando just genuinely had no idea how that kind of stuff works here. 10:22, 11 April 2020 (UTC)

Regarding USA Fahrenheit and non-USA Celsius preference, I was in Niagra Falls a few years back, listening to a Canadian station on the radio (ok, more than a few years ago...) and the DJ gave a weather report, saying “The current temperature is 25 degrees, that’s 77 on the understandable scale.” 04:22, 11 April 2020 (UTC)

I guess if you wanted to use the Newton scale you'd need to have Newton's original "degrees of heat" measuring device. 04:31, 11 April 2020 (UTC)

Nitpicking alert : the correct writing is "kelvin", not "Kelvin".

100°F is "really hot"? Maybe on a stripper... 13:00, 11 April 2020 (UTC)

Also nitpicking: "Kelvin" is correct, as it is a name like Fahrenheit (https://en.wikipedia.org/wiki/William_Thomson,_1st_Baron_Kelvin or https://en.wikipedia.org/wiki/River_Kelvin as you like...)Tier666 (talk) 14:59, 13 April 2020 (UTC)

Randall, as a physicist, should know about the equipartition theorem. It states that all degrees of freedom will carry the same average amount of energy in thermal equilibrium, not only the translational kinetic ones (but also rotational, and potential energies). It is technically not false to exclude some of these, but an arbitrary choice. I guess he just wanted to include the terms “translational” and “kinetic” to make sure it sounds ridiculously over-specific (which works well). 15:07, 11 April 2020 (UTC)

No, it's still an important distinction. Many Thermometers can only 'measure' the average Translational energy and the rotational and elastic energy is just assumed to match that. (The only Thermometers that measure rotational and elastic Energy are the ones who only measure their own temperature... which is 99.5 of all consumer Thermometers.) And it probably does except in some very specific cases with ultra high speed pressure changes.
Let's be scientific and [up things] before asserting false claims. Energies are not “assumed to match”, but it is the very core of Boltzmann's statistics that they have no other choice than doing so (that's one of the consequences of the second law of thermodynamics). That's why it is sufficient to know the first moment of any of the energy distributions to know about the thermal budget (definition of temperature). The way how thermometers measure temperature in practice is a totally different topic (take liquid thermometers: they exploit thermal expansion aka anharmonicity of inter-molecular potential energies). 16:29, 13 April 2020 (UTC)

+Using the average Translational Energy would would sidestep all the problems with the different units of temperature and would also eliminate the necessity of using the Boltzmann constant, simplyfying a lot of physics. But nobody wants to make the transition since most everyday temperatures would be between 5 and 8zJ, with 5 being freezing, six being tolerable and seven a desert at noon. The Unit, Zeejays would sound cool though. 09:30, 13 April 2020 (UTC)

Alternatively, use molar mean disordered translational kinetic energy per mole, making the numbers nicer by a factor of Avogadro's number, and bringing the scale to 2-3kJ/mol. Or add in a factor of 1.5 as well to make the gas K.E. formula simpler. Sqek (talk) 10:27, 13 April 2020 (UTC)
Eww, nobody likes (or uses) SI units in atomic physics. Contrary, electron-volts are a totally common measure of temperature. Think of the typical 25 meV of thermal neutrons off a research reactor. You literally see temperature (diffraction patterns on detectors), their De Broglie wavelengths are just in the inter-atomic distances range that makes them perfect diffraction probes of molecular/crystalline structure (weren't there these nasty radioactivity issues). 16:29, 13 April 2020 (UTC)

Well, it has Fahrenheit after a fashion. Just substract 460 from Rankine. It's even easier than converting Kelvin to Celsius!

I find it much quicker to subtract 0.01C° 27,315 times than to subtract 0.01F° 45,967 times, personally. I think you're quite barmy to suggest otherwise, Unsigned... :P 16:17, 11 April 2020 (UTC)
Now that I, the formerly Unsigned, think of it, I must agree with you - but for an entirely different reason. 273.15 in binary is a nice, round 100010001.001(00101) with 3 1's in the integer and 4+2n 1's for every 3+5n fractional digits, whereas 459.67 is much messier: 111001011.10110001111110... , with 6 1's in the integer alone. The more 1's there are in a number, the more operations you have to do for each addition or subtraction. So in binary, Kelvin-to-Celsius is much easier to convert than Rankine-to-Fahrenheit. Yet another point in favor of the glorious metric master system, da? Osato (talk) 19:57, 11 April 2020 (UTC)

I removed the weasel words, indicating that Fahrenheit is "generally appreciated" because 0 means very cold and 100 very hot. I adjusted it to "some claim" and adjusted the text to fit.

Make the scale in Celsius 0 to 200, and I think you would have a system much more relatable to Fahrenheit users. These Are Not The Comments You Are Looking For (talk) 04:16, 16 April 2020 (UTC)

I can imagine a worse scaling system! Base it on Cat-Scratch-Fever, Hot-Blooded, Yellow Snow, SpringTime in Alaska, Beds are Burning, Burning Down the House . (not in that order) Cellocgw (talk) 12:49, 13 April 2020 (UTC)

By a strange coincident, I went for a walk to the real Rømer's Observatorium Tusculanum today (full details in the Danish wiki). If you like Historical Science, it's worth a visit next time you're in Denmark... --Fod (talk) 16:25, 13 April 2020 (UTC)

I'm gonna annoy everyone by daring to point out that the traditional units are better for normal people than the metric system. Engineers and bureaucrats benefit from the metric system, because they convert units all the time, so the awkwardness of units being separated by ten is paid for by easy conversion. But for normal people, a binary system works better, with units as close together as possible, except in special cases where something else evolves spontaneously. And Celsius is the dumbest metric unit ever, without even the tenuous and illusory pretense of objectivity that other metric units have. Kazvorpal (talk) 16:42, 16 April 2020 (UTC)

The math markup is broken -GcGYSF(asterisk)P(vertical line)e (talk) 04:23, 27 March 2022 (UTC)

Thats a defective thermometer man theres only Celsius and Fahrenheit (talk) 17:12, 26 January 2024 (please sign your comments with ~~~~)